With the development of the future service, next generation wireless communication systems, such as 3GPP (third Generation Partnership Project) LTE (long term evolution) and beyond system, IMT-A (International Mobile Telecommunications-Advanced) system etc., are introduced to satisfy high speed, large capacity, and a high QoS (Quality of Service) for billions of subscribers. In this regard, efforts have been made to realize network-controlled D2D communications for reducing the load on the cellular communication network. Examples of such D2D communications include direct communications among a cluster of proximity devices, and autonomous D2D communications in a cellular network. In such network-controlled D2D communications, devices such as user equipments (UE) or terminals directly communicate with each other, instead of conveying data from one device to the other via the cellular network (in particular via an access node or base station thereof), wherein primary control and configurations, such as channel/bearer configurations, may be carried out by the cellular network.
Security protection may be an issue for the network-controlled D2D communications, for example, because malicious users may be able to eavesdrop on the D2D communication if no strong security protection between peer UEs conducting a direct D2D communication is used. According to the current security mechanism, the key generation for network-controlled D2D communications are managed and controlled by the core network. The core network, especially apparatus for key management (such as MME (Mobility Management Entity), HSS (Home Subscriber Server), and/or the like) needs to be involved in an establishment and key negotiation of every D2D connection. This may highly increase the signaling burden of the core network, for example in a case that the number of UEs conducting D2D communications is huge.
An enhanced security key generation method has been proposed to enable the D2D security key generation without involving a core network, which provides a basic feasible solution for D2D security key handling. However, this solution is provided to solve the problem in intra-eNB cases where both of the D2D pairs are under a same eNB or D2D area. The key generation, especially key pairing in the scenario where D2D devices are under different eNBs or D2D areas, is not considered yet. In view of this, it would be advancement in the art to provide an approach of key pairing for D2D devices under different eNBs or D2D areas.